Literally means the exact opposite, the furthest thing from nice. Used as a conversation stopper when you when you are too scared to call a friend out on their shit but just pray they don't give you any more details. Bonus points if you send it over text, extra bonus points if it is over two separate texts.
Bro 1: yo dude I made out with your ex last night.
A Shackteau is a humble, weather-beaten, structurally questionable shelter located in a spectacular or highly coveted place—Wales, Jackson Hole, Sun Valley, Crested Butte, coastal Maine, the Alps—where the building itself may be worth almost nothing, but the dirt, view, access, and mythology make it absurdly valuable.
In use:
Shackteâu - We thought it was an abandoned shed until the realtor called it a rare alpine Shackteâu with unobstructed views and listed it for $2 million.